There are 10 bulbs in room, 4 of them are fused. The probability that the room will be lighted on pressing the switches of any three

There are 15 bulbs in a room. Each one of them can be operated independently . The number of ways in which the room can be lighted is

A room has 4 sockets for electric lamps. From a collection of 11 light bulbs of which 6 are good, 4 bulbs are selected at random and put in the sockets. Find the probability that the room does not suffer from a complete black-out.

A room contains 3 sockets for bulbs. If from a collection of 10 bulbs, out of which 6 are defective, 3 bulbs are selected at random and put in the sockets, then the probability that the room is lighted is

In a room there are 12 bulbs of the same wattage,each having separate switch.The number of ways to light the room with different amounts of illumination is (a) 12^(2)-1 (b) 2^(12) (c) 2^(12)-1 (d) none of these

Assertion : If an electric fan be switched on in a closed room, the air of the room will be cooled. Reason : Fan air decrease the temperature of the room.